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New tailor-made PHB-based nanocomposites for high performance applications produced from environmentally friendly production routes

Final Report Summary - BUGWORKERS (New tailor-made PHB-based nanocomposites for high performance applications produced from environmentally friendly production routes)

Executive Summary:
BUGWORKERS Consortium developed a new cost-competitive and environmentally friendly bionanocomposite material based on the combination of a polyhydroxybutyrate (PHB) matrix with new chemical, structure produced by new fermentation culture technology with two types of nanofibres,cellulose whiskers and lignin-based, in order to have a true alternative to engineering materials in two main sectors: household appliances, computers & telecommunications applications.

To fulfil this global objective, current limitations of PHB polymers and their composites were overcome using a synergic combination of different approaches:

•A tailor-made PHB biopolymer structure obtained using new fermentation culture conditions, i.e by synergic combination of different media and precursor feedings (specific sugar blends) obtained from hydrolyzed bio-mass, in particular agricultural subproducts feedstock (whet straw), being able to select a structure to provide a PHB with enhanced functionalities (improved thermal and chemical properties, cellulose compatibility, processing, higher impact,..) in comparison with commercial ones.

•To improve the cost competitiveness of PHB biopolymer by optimization of the fermentation process (increasing yield) and the use of lingo-cellulose biomass and other industrial by-products as fermentation feedstock. It will be no competition with food supply.

•Development of cellulose whiskers and lignin nanofibres using enzymatic production routes with new functionalities (antimicrobial, flame retardant and self-assembly) from wood waste.

•Compounding of new PHB with a synergic combination of both types of nanofibres and long natural fibres, using the screw extruder for improved nanofibres distribution, reducing thermal degradation,improve matrix-nanofibre interphase and introduction of coupling agents by reactive extrusion.

•Development of multilayer structures (co-extrusion and co-injection) in order to obtain multifunctional material properties to improve the final performance of plastic parts in select sectors.

Project Context and Objectives:
The major achievements of the project during its duration have been the following:

Development of sugar production from lignocellulosic waste and characterisation of sugar pattern. A conversion process from wheat straw to concentrated hydrolysate was developed. The final hydrolysate had a high sugar concentration with negligible amounts of inhibitors.

Figure 1. Scheme of the sugar production process from biomass

Production of PHB by fermentation processes. A process was implemented with a strain that metabolizes C6 and C5 carbohydrates. The parameters positively influencing P(3HB) accumulation were identified (levels of phosphate and pH). Excellent yields and productivities were reached, around 1.6 g P(3HB)/(L∙h).
Upscaling of the homopolymer P(3HB) production was successfully achieved. First, optimisation of PHB homopolymer production was performed at 30L-scale reactors and later upscaled satisfactorily to the 250L-scale.

Figure 2. 250L fermenter for PHB production.

Production of P(3HB-co-4HB) copolymers at laboratory level. Bacterial fermentation of copolymers was studied, developed and optimised at bench-scale. Copolymers with different ratios of 4HB were produced successfully ranging from 2.4% 4HB to 7.2% 4HB. Properties of these copolymers were also measured and analysed.

Figure 3. Film of P(3HB-co-4HB) with 7% 4HB.

Development of a novel down-streaming progress using alternative green solvents. Alternative green solvents were used for the extraction and purification of both PHB homopolymer and the P(3HB-co-4HB) copolymers. These trials showed promising results and proved that it is possible to have alternatives to the use of high volumes of chloroform in PHB purification and extraction.

Process development and establishment of optimised procedures for obtaining nano-sized materials from lignocelluloses. Optimised and Economically Feasible Procedures for Obtaining Nanofibres were developed for two types of nanocellulosic fillers: cellulose nanowhiskers (CNW) and nanolignin (NL). These nanofillers were later used in compounding for the production of PHB-based nanocomposites.

Figure 4. Microscopic view of nanocellulosic materials.

Development and production of optimised PHB formulations. A two-step compounding technology was developed for PHB formulation. Two different PHB formulations were developed for the production of the different case-studies. The first formulation, based on a blend of PHB with PBS was successfully used for the production of injection moulding parts. The second formulation, containing talc, may be used also for extrusion and thermoforming, besides injection moulding.
Also, novel compounding technologies with improved mixing were designed, manufactured and tested in order to produce PHB-based nanocomposites.

Figure 5. PHB compound developed by AIMPLAS.

Complex multilayer parts produced by injection moulding and extrusion + thermoforming. Several demonstrator parts consisting of complex multilayer structures were successfully developed, produced and tested.

Figure 6. Complex co-injected part (spinning top) and complex injected part (socket) produced in the project.

Industrial case studies developed and produced. Four different industrial case-studies were chosen: an egg-box and a compressor cover for a refrigerator (household sector) and a microphone holder and a button rod for a door entry system (electronic communication devices sector). Demonstrator parts were moulded and tested, fulfilling the most critical requirements for the applications, such as processability, dimensional stability and accuracy, endurance, drop tests and food contact suitability.

Figure 7. Egg-box and microphone holder produced in the project with different PHB formulations.

Economic, logistic, environmental and health evaluation. A thorough logistic and economic study was carried out taking into account several critical issues. The cost range of the PHB compound developed in the project will range from 4 to 10 €/kg, which is a competitive cost. The environmental study comprised the study of biodegradability as well as the long-term properties. Safety and health evaluation was also carried out in compliance with safety regulations applying to the material and processes developed.

For more info, visit the project web site:

Project Results:
The work in the project has been structured as shown in Workpackages (figure 1 of the S&T figures)
Definition of PHB-nanocomposites properties and application
Development of low cost PHB homo and copolymers
Enzymatic production of lignin nanoparticles and cellullose wishkers
Preparation of PHB based-nanocomposites using low shear devices
Study of Multilayer structures processability (co-extrusion-thermofirming & co-injection)
Application development and industrial case-studies
Economic, logistic, environmental and health evaluation
The main scientific and technological results achieved are detailed in next points:
1. New chemical structure of PHB fermented from industrial or agricultural by-products increasing the PHB yield in at least 30% using non-food sugar as feedstock, reducing the current PHB cost in at least 70%, increasing the PHB-cellulose and lignin compatibility, improving resistance to water-cleaning agents and improving the PHB processing window.
2. Development of nanoparticles from lignocellulose by-products: providing antibacterial and antifungal properties, self assembly capacity and cost competitive
3. Compounding of new PHB and nanoparticles using the planetary multi-screw extruder in order to improve nanoparticles distribution, minimize thermal degradation, improve matrix-nanofibre adhesion
4. Introducing suitable coupling agents by reactive extrusion to improve compatibility
5. Bionanocomposite with tailor made properties made from biomass close to 100 % by weight, increase thermal resistance of PHB nanocomposites in at least 15ºC, mechanical properties at least 50 % and better fire resistance UL94-V2 grade
6. Development of multilayer structures (co-extrusion-thermoforming and co-injection) in order to obtain multifunctional material properties suitable to replace engineering materials and reducing a weight by more than 10% without reduction of mechanical and thermal properties.

This information is presented below more detail and on a WP basis (in the attachment )

Potential Impact:
The development of a biodegradable polymer from non-food renewable sources could have a great impact on the wide introduction of biopolymers into traditional markets. Also, obtaining PHB from an agro-industrial residue has a very positive effect both on the cost and on the environmental impact of the developed material. Also, the development of novel technologies for extraction and purification of PHB have a very positive effect on the environmental impact of PHB production, which currently involves the use of high amounts of harmful solvents such as chloroform.

Pre-industrial scale processes to obtain nanofibres and nanoparticles from lignocelluloses have also been developed. Extending this technologies to residual raw materials could be an interest for industries such as the paper industry with high volumes of lignocellulosic residues.

The possibility of formulating the PHB with other materials widens the range of applications, extending the possibilities of using the material developed in BUGWORKERS into other markets such as packaging or biomedical applications. Also, in this sense, processability of the material has been significantly improved.

List of Websites:

Coordinator: AIMPLAS - Instituto Tecnológico del Plástico
C/ Gustave Eiffel, 4 (València Parc Tecnològic)
46980 - PATERNA (Valencia) – SPAIN
Tlf. (+34) 96 136 60 40